374 The Upper Devonian Deposits of Maryland 



Total 

 Thick- thick- 

 ness, ness. 

 one which he called the Upper Chemung and stated that, " The 



exposure of this rock in place is incomplete, but great masses of 

 conglomerate are strewn thickly over the surface." ' The occur- 

 rence of the Upper Chemung conglomerate at the locality just cited, 

 only IVz miles northeast of the Jennings Run conglomerate and in 

 the direct line of strike supports the opinion that they are 

 identical. 



In Dr. White's section along the Potomac River to the northwest 

 of Keyser where the same belt of the Jennings formation crosses 

 the river he described two layers of conglomerate in the Chemung 

 about 900 feet apart. The upper one is given as 400 feet below the 

 top of the Chemung and 2 feet in thickness and is described as 

 " composed of very thin, flat, rounded quartz pebbles. In a matrix 

 of coarse rotten sand with numerous fossil shells Imbedded " while 

 the lower one is given as 40 feet thick and consisting of " a gray, 

 hard sandstone, containing numerous layers filled with flattish, 

 white quartz pebbles."'' The interval of 900 feet between these 

 two conglomerates agrees closely with that of 950 feet given by 

 Professor Stevenson as the thickness of the rocks between his 

 lower and upper Chemung conglomerates in Fulton County, Penn- 

 sylvania.^ 



The horizontal distance was obtained in part from pacing and 

 also by counting railroad ties parallel to the direction of the section 

 from which was estimated .1225 feet for the thickness of the rocks 

 from the base of the Jennings formation to the top of this con- 

 glomerate. Dr. Rowe made the horizontal distance by pacing 3236 

 feet which with an average dip of 77° gave a thickness of 3140 

 feet from the base of the Jennings to the top of this conglomerate. 



No. 10. For a distance of about 630 feet along the highway are 

 partial exposures of coarse grained micaceous, greenish-gray and 

 brownish-red sandstones alternating with shales. The average dip 

 is about 62° and at the top of the Chemung it is 57°. The greenish 

 to yellowish sandstones contain some rather poorly preserved 

 Chemung fossils, as for example Spirifer disjunctus Sowerby and 

 Spirifer mesacostalis Hall (?) together with Grammysia elliptica 

 Hall and Sphenotvs contractus Hall. The last of the fossils were 

 poorly preserved and occurred after a considerable thickness of 

 brownish-red rocks had been passed. On Dr. Rowe's section the 

 horizontal distance from the top of the conglomerate to the upper 

 horizon of fossils was 612 feet which with an average dip of 68° 

 gave a thickness of 570 feet for this upper zone of the Chemung. . 555 3780 



^Ibid., p. 99. 



= Proc. Amer. Phil. Soc, Vol. XIX. 1882, p. 443. 



= 2d Geol. Surv., Pa., T-, p. 75. 



